Method for manufacturing heat pipe with artery pipe

ABSTRACT

An exemplary method for manufacturing a heat pipe includes the following steps: providing a tube, a mandrel and an artery pipe, the tube defining an opening at one end thereof, a wick structure being positioned on an inner surface of the tube, a slot being defined in an outer surface of the mandrel; inserting the mandrel and the artery pipe into the tube via the opening, the artery pipe being received in the slot; baking the tube with the mandrel and the artery pipe to make the artery pipe join the wick structure; drawing the mandrel out of the tube via the opening; and injecting a working media into the tube, and evacuating and sealing the tube.

BACKGROUND

1. Technical Field

The disclosure generally relates to a method for manufacturing a heatpipe, and particularly to a method for manufacturing a heat pipe with anartery pipe.

2. Description of Related Art

Heat pipes are widely used in various fields for heat dissipationpurposes due to their excellent heat transfer performance. Currently, atypical heat pipe includes a sealed tube made of thermally conductivematerial and a working fluid contained in the tube. The working fluid isemployed to carry heat from one end of the tube, typically called an“evaporator section,” to the other end of the tube, typically called a“condenser section.” Preferably, a wick structure is provided inside theheat pipe, lining an inner wall of the tube, for drawing the workingfluid back to the evaporator section after it is condensed at thecondenser section.

During operation, the evaporator section of the heat pipe is maintainedin thermal contact with a heat-generating component. The working fluidcontained at the evaporator section absorbs heat generated by theheat-generating component and then turns into vapor. Due to thedifference of vapor pressure between the two sections of the heat pipe,the generated vapor moves and thus carries the heat towards thecondenser section where the vapor is condensed into condensate afterreleasing the heat into ambient environment via, for example, finsthermally contacting the condenser section. Due to the difference incapillary pressure which develops in the wick structure between the twosections, the condensate is then drawn back by the wick structure to theevaporator section where it is again available for evaporation.

Usually, an artery pipe is provided inside the heat pipe. The arterypipe enhances the capillary force to draw the condensate back andthereby avoid dry-out of the heat pipe. The artery pipe is sealed withinthe tube of the heat pipe, but is unfixed and can move freely in thetube. This can adversely affect vapor flow in the heat pipe. Inaddition, when such a heat pipe needs to be flattened to increase acontact surface with the heat-generating component, it is impracticableto ensure that the artery pipe is attached on a portion of the tube ofthe heat pipe aligning with the heat-generating component. Thus theperformance of the heat pipe may be adversely affected.

What is needed, therefore, is a method for manufacturing a heat pipewhich can overcome the described limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present embodiments.Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a flow chart showing a method for manufacturing a heat pipe inaccordance with one embodiment of the disclosure.

FIG. 2 is an exploded, isometric view of a tube, a cylindrical mandreland an artery pipe used for manufacturing the heat pipe of FIG. 1.

FIG. 3 is similar to FIG. 2, but showing the cylindrical mandrelinserted in the tube, and the artery pipe still out of the tube.

FIG. 4 is similar to FIG. 3, but showing the artery pipe inserted in thetube after the cylindrical mandrel has been inserted in the tube.

FIG. 5 is a cross sectional view of the tube of FIG. 4, taken along lineV-V thereof.

FIG. 6 is similar to FIG. 4, but with the cylindrical mandrel have beenremoved from the tube, and showing the tube marked.

FIG. 7 is similar to FIG. 6, but showing the tube flattened.

FIG. 8 is a cross sectional view of the tube of FIG. 7, taken along lineVIII-VIII thereof.

FIG. 9 is an isometric view of a tube, a cylindrical mandrel and arterypipes used for manufacturing a heat pipe with a plurality of arterypipes.

DETAILED DESCRIPTION

FIG. 1 summarizes a method for manufacturing a heat pipe in accordancewith one embodiment of the disclosure. The method is explained in detailas follows:

Referring also to FIG. 2, firstly, a tube 10, a cylindrical mandrel 20and an artery pipe 30 are provided. The tube 10 is hollow andcylindrical, and is made of highly heat conductive metal, such ascopper, and so on. The tube 10 defines an opening 11 at one end thereof.A wick structure 12 is layered on an inner surface of the tube 10. Thewick structure 12 can be fine grooves defined in the inner surface ofthe tube 10, screen mesh or fiber inserted into the tube 10 and heldagainst the inner surface of the tube 10, or sintered powders bonded tothe inner surface of the tube 10 by a sintering process. The cylindricalmandrel 20 is made of metal which has high rigidity, a high meltingpoint and low reactivity, such as steel, and so on. The mandrel 20defines a longitudinal slot 21 in an outer surface thereof. The slot 21extends through to both a front end surface and a rear end surface ofthe mandrel 20. A cross section of the slot 21 defines part of anellipse. An outer diameter of the mandrel 20 is substantially equal toan inner diameter of the tube 10 with the wick structure 12 therein, anda length of the mandrel 20 is greater than that of the tube 10. Theartery pipe 30 is hollow and cylindrical, and defines a channel 31therein. A cross section of the artery pipe 30 is annular. The arterypipe 30 has an outer diameter slightly less than a width of the slot 21of the mandrel 20, but greater than a depth of the slot 21 of themandrel 20. The artery pipe 30 has a length substantially equal to thatof the tube 10. The artery pipe 30 is formed by a plurality of copperwires woven together, each of the copper wires having a diameter ofabout 0.05 mm.

Referring also to FIG. 3, the mandrel 20 is inserted into the tube 10via the opening 11, with one end of the mandrel 20 exposed out of thetube 10. An outer circumferential surface of the mandrel 20 isintimately in contact with the wick structure 12 of the tube 10. Inparticular, when the wick structure 12 is a screen mesh or fiber wick,or a sintered powder wick, the mandrel 20 can provide required pressureto compel the wick structure 12 to intimately contact the inner surfaceof the tube 10. Thus, heat generated by a heat-generating component (notshown) is transferred to the wick structure 12 from the tube 10 moreeasily.

Referring also to FIG. 4, the artery pipe 30 is horizontally insertedinto the slot 21 and then moves along the slot 21 into the tube 10.Since the diameter of the artery pipe 30 is slightly greater than thedepth of the slot 21, when the artery pipe 30 enters the tube 10, theartery pipe 30 is pressed by both the wick structure 12 and the mandrel20 and thereby deforms slightly. Thus, when the artery pipe 30 isinserted in the tube 10, the artery pipe 30 is deformed to intimatelycontact with the wick structure 12. Referring also to FIG. 5, after theartery pipe 30 is inserted in the tube 10, the artery pipe 30 has anelliptic cross-section, and forms an arcuate contact surface 33 abuttingthe wick structure 12. A contact area between the contact surface 33 ofthe artery pipe 30 and the wick structure 12 is increased after theartery pipe 30 is deformed, whereby the capillary force generated by theartery pipe 30 and the wick structure 12 is improved.

The tube 10 with the mandrel 20 and the artery pipe 30 is then heated ina high temperature furnace (not shown) to make the artery pipe 30 joinwith the wick structure 12. During heating, the mandrel 20 is kept inthe tube 10 to ensure that the artery pipe 30 is straight and extendsalong a longitudinal direction of the tube 10, and further ensure thatthe artery pipe 30 intimately contacts the wick structure 12.

Referring to FIG. 6, after the artery pipe 10 is baked to combine withthe wick 12 of the tube 10, the mandrel 20 is drawn out of the tube 10via the opening 11 of the tube 10. A marking 40 is engraved on an outercircumferential surface of each end of the tube 10, corresponding to aposition of the artery pipe 30. Alternatively, the marking 40 can beformed on only one end of the tube 10 or at a middle of the tube 10.

Subsequent processes such as injecting a working media into the tube 10,and evacuating and sealing the tube 10, can be performed usingconventional methods. Thus, a straight circular heat pipe is attained. Aportion of the tube 10, where the markings 40 are formed, is finallyflattened to form a flat-type heat pipe 50 which has a rectangularcross-section, as shown in FIGS. 7 and 8. The heat pipe 50 includes atop surface 51, and a bottom surface 52 in parallel with the top surface51. The top and bottom surfaces 51, 52 are planar. The markings 40 arelocated on a middle axis (not shown) of the top surface 51, and theartery pipe 30 is aligned with the middle axis of the top surface 51.

In use, the top surface 51 of the heat pipe 50, with the markings 40, isattached to the heat-generating component. At this time, the artery pipe30 aligns with the heat-generating component.

In the present method for manufacturing the heat pipe 50, the slot 21 isdefined in the mandrel 20. Thus, the artery pipe 30 is accurately fixedon the wick structure 12 of the tube 10, in an orientation whereby alength of the artery pipe 30 is fixed along a corresponding length ofthe wick structure 12. The artery pipe 30 cannot move freely in the tube10. This increases the flow of the working media in the tube 10, andimproves the heat transfer performance of the heat pipe 50. In addition,the markings 40 are formed on the circumferential surface of the tube10, and align with the artery pipe 30. Accordingly, it is easy toascertain the position of the artery pipe 30 according to the markings40. In use, the position of the heat pipe 50 can be adjusted to makesure that the artery pipe 30 aligns with the heat-generating component,by using the markings 40 as guides. This further ensures the best heattransfer performance of the heat pipe 50.

In alternative embodiments, the shape and size of the slot 21 of themandrel 20 can be varied, thereby forming different kinds of arterypipes 30 in the heat pipe 50 to satisfy different heat dissipationrequirements. Furthermore, the mandrel 20 can have more than one slot21, so that more than one artery pipe 30 is fixed in the tube 10. Theembodiment described below includes one example of such variations.

Referring to FIG. 9, in this embodiment, a mandrel 20 a longitudinallydefines three slots 21 a in an outer circumferential surface thereof.Two of the slots 21 a are at one end of the mandrel 20 a, and the otherslot 21 a is at the other opposite end of the mandrel 20 a. Each of theslots 21 a has a length less than that of the mandrel 20 a. Each of theslots 21 a accommodates one artery pipe 30 a. Thus, the heat pipemanufactured via this method includes three artery pipes 30 a in thetube 10, wherein two artery pipes 30 a are attached to one end of thewick structure 12, and another artery pipe 30 a is attached to the otheropposite end of the wick structure 12.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present embodiments have been setforth in the foregoing description, together with details of thestructures and functions of the embodiments, the disclosure isillustrative only, and changes may be made in detail, especially inmatters of shape, size, and arrangement of parts within the principlesof the invention to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.

What is claimed is:
 1. A method for manufacturing a heat pipe,comprising: providing a tube, a mandrel and at least one artery pipe,the tube defining an opening at one end thereof, a wick structure beingpositioned on an inner surface of the tube, at least one slot beingdefined in an outer surface of the mandrel; inserting the mandrel andthe at least one artery pipe into the tube via the opening, the at leastone artery pipe being received in the at least one slot; baking the tubewith the mandrel and the at least one artery pipe to make the at leastone artery pipe join the wick structure; drawing the mandrel out of thetube via the opening; and injecting a working media into the tube, andevacuating and sealing the tube.
 2. The method for manufacturing a heatpipe of claim 1, further comprising forming at least one marking on anouter surface of the tube at a position corresponding to the at leastone artery pipe.
 3. The method for manufacturing a heat pipe of claim 2,wherein the at least one marking comprises two markings formed at twoends of the tube, respectively.
 4. The method for manufacturing a heatpipe of claim 2, further comprising flattening the tube at a positionwhere the at least one marking is formed.
 5. The method formanufacturing a heat pipe of claim 1, wherein the at least one slot ofthe mandrel has an elliptic cross-section, the at least one artery pipebeing hollow and cylindrical, and having an outer diameter slightly lessthan a width of the at least one slot of the mandrel, but greater than adepth of the at least one slot of the mandrel, the at least one arterypipe being pressed by the wick structure and the mandrel to deformslightly when the at least one artery pipe and the mandrel are in thetube.
 6. The method for manufacturing a heat pipe of claim 1, whereinthe at least one slot is longitudinally defined in an outercircumferential surface of the mandrel, and extends through a front endsurface and a rear end surface of the mandrel.
 7. The method formanufacturing a heat pipe of claim 1, wherein the at least one slotcomprises a plurality of slots located at two ends of the mandrel,respectively.
 8. The method for manufacturing a heat pipe of claim 1,wherein the at least one artery pipe is formed by a plurality of metalwires woven together.
 9. The method for manufacturing a heat pipe ofclaim 1, wherein the mandrel has an outer diameter substantially equalto an inner diameter of the tube with the wick structure, and a lengthgreater than that of the tube.